The present invention relates to a drive mechanism for a rotary element, such as a rotary table, in which the drive mechanism engages the table circumference. Such rotary elements are used in various machines and in devices for angular adjustment or angular measurement.
It is a known practice to drive a rotary table from beneath the table by means of a compensating coupling secured to the axis of rotation of the table. This approach may isolate the table from transverse drive forces, but it is not always applicable, for it requires that the rotary table be accessible from below.
Another known practice is to drive a round table laterally. This approach, however, may apply transverse forces to the table, for any uncompensated drive foces must be absorbed by the table bearing. Such drive forces may produce deformations in the rotary bearings which may result in reduced precision of operation.
Swiss patent No. 538,110 discloses a lateral rotary table drive in which a drive rim provided on the table is clamped between a drive element and an opposed supporting element and both the drive element and the supporting element are aligned along a radius of the table. The drive element and the supporting element are both freely shiftable along the radial direction and are resiliently biased toward each other against the table rim. In this way no net radial force is exerted on the table bearing by the drive mechanism along the radius extending between the drive element and the table center; however, unbalanced forces are applied to the table rim in the direction perpendicular to the radius and these unbalanced forces must be absorbed by the table bearing.